An alarming rise in the number of young Iranians who are shunning marriage prompted an unprecedented step from the government on Monday, with officials launching a matchmaking website.

The move comes amid deep alarm in the Islamic republic, where sex outside marriage is forbidden, that family values are under threat and fears that the population could eventually fall.

At pains to point out it was not offering an online dating service, officials said the "Find Your Equal" website hoped to reverse a surge in young Iranian adults, currently 11 million, who are still single.

It will do so by using a network of matchmakers -- clerics and people of good standing in their communities, such as doctors, teachers or other professionals -- to pair people off.

Having trialled the system for a year, during which it said 130 such intermediaries had introduced 3,000 men and women -- with 100 couples getting married -- it will now launch fully.

The aim is for 100,000 marriages over the next 12 months.

"We face a family crisis in Iran and we are sensitive about this," Mahmoud Golzari, a deputy minister for sport and youth, told reporters when unveiling the plan in Tehran.

"There are many people who are single, and when that happens it means no families and no children," he said, defending the need for the website.

"This should have happened a long time ago."

Under the plan, a young man or woman will register online and the matchmaker will try to come up with a suitable partner from its database.

Family meetings, and even psychological testing to ensure a pair are compatible, will follow.

"We are using modern technology to solve a problem, though our difficulties are different from in Western countries," Golzari said.

"Our Islamic and Iranian culture does not approve of long-term relationships out of wedlock, in which people become friends and after a long period of time, maybe they get married or maybe not."

Many young Iranians cite the country's strict social mores and pressure to get married as a heavy burden.

Economic factors, such as high youth unemployment, are also blamed for rising marriage ages -- currently 30.6 for men and 26.7 for women in Tehran.

Religious families also blame a Western cultural invasion for eroding traditional values in a country where, even for young adults, the family is core; most singles live at home.

Zohre Hosseini, project manager for the matchmaking website, acknowledged that young people faced difficulties.

"We don't claim that we are solving all the problems," she said.

"But the problem we are tackling here is that of finding a partner."

Although online dating sites are banned in Iran, around 350 operate illegally. Millions of young adults also use Facebook and social media to hook up despite such sites being prohibited.